1. Field of the Invention
This invention relates to a fuel injection method in an electronically controlled engine for calculating fuel injection amounts by the use of a microprocessor.
2. Description of the Prior Art
In abrupt deceleration or the like, a measuring plate of an air flow meter produces undershoot, and intake air flow detected from the output of the air flow meter is remarkably smaller than actual intake air flow so that the fuel injection amount calculated on the basis of the output of the air flow meter has a very small value, causing a misfire. Thus, to avoid such misfire, the minimum fuel injection amount is determined and, when the calculated fuel injection amount is smaller than the minimum fuel injection amount, the fuel injection amount is made to be the minimum fuel injection amount. In the prior fuel injection method, however, the minimum fuel injection amount was constant irrespectively of the running condition of an engine. Since the minimum fuel injection amount capable of avoiding misfire varies with the running condition of the engine, when the minimum fuel injection amount is determined so as not to adversely affect driveability of the vehicle in the prior fuel injection method, noxious components in exhaust gas increase and efficiency of fuel consumption is degraded under a predetermined running condition of the engine. On the other hand, when the minimum fuel injection amount is determined so as to restrain the noxious amount of components in the exhaust gas, the driveability is degraded under another predetermined running condition of the engine.